1. Field of the Invention
The present invention relates to a lens barrel such as a photographing (imaging) lens which incorporates a rotatable ring performing an advancing/retracting operation in which the rotatable ring rotates while moving along an optical axis, and a fixed-position rotating operation in which the rotatable ring rotates at an axial fixed position without moving along the optical axis.
2. Description of the Related Art
Retractable photographing lenses in which a rotatable ring such as a cam ring advances along an optical axis while rotating from a fully retracted position toward a ready-to-photograph position (e.g., zooming range of zoom lens) upon power being turned ON and in which the cam ring stops advancing upon reaching the ready-to-photograph position to be rotatable at an axial fixed position on the optical axis without rotating are known in the art. In such known retractable photographing lenses, a drive mechanism for driving the rotatable ring is generally complicated and large in size.